The present invention relates to drip irrigation hoses, and to methods and apparatus for making such hoses.
Drip irrigation hoses are increasingly being used for irrigating various types of plants since they supply the water directly to the root regions of the plants, and therefore are highly conservative of water resources. One type of irrigation hose is constructed by simultaneously extruding a plastic hose and bonding to its inner surface a plurality of emitter elements, or a strip of emitters, spaced longitudinally of the hose for discharging the water at a slow rate via discharge openings formed in the hose. Another type includes a sheet of flexible plastic material formed into a seamed hose, with the emitter elements bonded within the seam or to another part of the hose for discharging the water at a slow rate through discharge openings in the hose. The present invention is applicable to both types of drip irrigation hoses.
Examples of drip irrigation hoses of these types are described in U.S. Pat. Nos. 4,196,853; 5,163,622; 5,183,208; 5,203,503; 5,246,171; 5,333,793; 5,522,551; 5,620,143; 5,695,127; 5,785,785 and 6,027,048.
One problem in using drip irrigation hoses is the difficulty in ensuring relatively uniform discharge rates along the length of the hose. This problem is particularly acute where extremely long lengths of the hose are used since the hose itself produces a pressure drop along its length tending to decrease the discharge rate of the emitters at the end of the hose. This sensitivity of the discharge rate to the water pressure is also a problem where the land being irrigated is not flat and even.
Another problem with such drip irrigation hoses is sensitivity to clogging, and the difficulty in dislodging clogging particles.
In addition, such drip irrigation hoses are frequently used for only a single season, or for relatively few seasons. Accordingly, the cost involved in producing such drip irrigation hoses is a significant factor in their use.